Short–time-scale evidence for strong Langmuir turbulence during hf heating of the ionosphere

Results of short-pulse, low--duty-cycle hf-heating experiments are shown to agree with predictions of a model of correlated, localized cavitons which undergo cycles of nucleation, collapse, and burnout. Predicted ``free-mode'' spectral features associated with the radiation of Langmuir waves from collapsing cavitons are observed. Single radar pulse data provide evidence that temporal correlations between caviton events are present at early times following the onset of heating.